New build mini Mill

[joeavaerage]

Hi,

Those prices are above my budget. Do you think that price is normal?

Yes they are normal.

You might pay $150USD for a C7, that is rolled, ballscrew say 2005 by 1m long including bearing blocks, and you'd pay about $1500USD for the same screw but ground
to C5 grade and more again to get C3 grade.

I understand that you want ground ballscrews....I did too, and I bought them, but sceondhand because, like you they are beyond my budget to buy new.
That's why I posted that link to dyGlobal....that's where I buy parts from. I got a complete set (3) THK C5 32mm double nut (BNFN) WITH two FK25 bearing blocks per
screw for $1800NZD ($1260USD) which included three day shipping to New Zealand from Korea. They are superb!!!

If you don't have budget to buy new C5's then you can't afford to overlook secondhand.

Craig

[joeavaerage]

Hi,
now that you see that there is nearly a ten-fold increase in price between C7's, best rolled grade, to C5's the entry level ground grade you need to
understand the difference between the two.

Firstly the C7, C5, C3 etc grades are a Japanese Industrial Standard that's become so widely used that it's understood around the
globe. Having said that there are DIN standards also, which we may come back to.

THK and NSK have extensive catalogues with good application notes covering accuracy grades and pre-load grades....well worthwhile to download and
read if you want to understand about ballscrews.

A C7 screw is good to 50um (0.05mm) over 300mm....which is pretty damn good, especially for the price. Where they fall down is cyclic error.
Cyclic error is the deviation form theoretical best over 360 degree (2.PI radians) rotation of the screw, and for C7 its 35um (0.035mm).

A C5 screw is good to 18um (0.018mm) over 300mm, so better than C7, but not hugely so, but cyclic error is 8um (0.008mm) max. Its cyclic error where ground screws
really shine....but....MAN....are they expensive!! C3's are worse and C1's and C0's are special order and I've never seen them for sale, new or secondhand.

There is one brand that deserves mention, SKF, a German brand. They make a range of screws by first rolling them but then grinding them.
They are roughly intermediate to C7's and C5's. I think this is because they follow DIN standards, but the basic accuracy is 23um (0.023mm) per 300mm and about
18um (0.018mm) cyclic. If you can find these screws, and as you are in Europe you'll have better luck than I, especially if you can find them secondhand they represent
a good choice of quality without breaking the bank, not that German stuff is ever cheap.

Its time to put your thinking cap on. If you want a good and accurate machine then ground screws are the obvious choice, but they in turn will determine many of the other choices
you will have to make throughout the design and build. For instance you wouldn't go and spend big bucks on C5 screws but then use cheap, flexy linear guides, or crap
steppers or servos....it just does not make sense.

On the other hand if you reasonably say that 'my budget is not enough for ground screws' then you can relax a little some of the other requirements, or possibly re-direct your funds to a
rather more rigid machine even if it screws aren't top class. Rigidity is always the hardest to achieve with home-builds.

Probably the majority of home-built routers and mills use rolled screws, and for wood and plastics the accuracy is every bit good enough. If you want to make precise engineering parts
then you talking a different machine, and way WAY WAY more expensive.

Craig

[StrawberryBoi]

Alright, so Hiwin reported back that even their 'in-stock' C6 rolled options would have a 6-8 month lead time. They also told me the FSC nuts are not preloaded and I'm waiting to hear back on a recommendation for a preloaded single nut solution (their website listed it as preloaded so I want it from the horses mouth, so to speak).

It may be that Hiwin is not currently running ground screws due to pandemic related issues, they are trying really hard to avoid quoting a C3 screw at any price-point. Alternatively there could be a trade related issue to the USA I'm not aware of. This courtesy of their vendor MotionUSA.com, whom HiwinUSA directed me to.

[mactec54]

Alright, so Hiwin reported back that even their 'in-stock' C6 rolled options would have a 6-8 month lead time. They also told me the FSC nuts are not preloaded and I'm waiting to hear back on a recommendation for a preloaded single nut solution (their website listed it as preloaded so I want it from the horses mouth, so to speak).

It may be that Hiwin is not currently running ground screws due to pandemic related issues, they are trying really hard to avoid quoting a C3 screw at any price-point. Alternatively there could be a trade related issue to the USA I'm not aware of. This courtesy of their vendor MotionUSA.com, whom HiwinUSA directed me to.

If you can't get what you want then try THK or NSK, NSK are made in the USA if custom you may have to wait THK the same you may have to wait there are so many to chose from don't get stuck on Hiwin

Some Chinese Ballscrews are quite good as well TBI Motion and BST Motion, TBI Motion would be my pick if I needed to get some cheaper Ballscrews they do Ground Ballscrews and Rolled

[joeavaerage]

Hi,

Automation Overstock, surplus automation equipment, overstock automation devices, manufacturer overruns, linear bearings, variable speed drives, circuit breakers, contactors, starters, relays

Craig